Objective: Magnetic Resonance-guided focused ultrasound surgery (MRgFUS) is a non-invasive treatment for uterine fibroids. Fibroid intensity in pre-treatment MRI showed high correlation with post-treatment non-perfused volumes (NPV), and serves as an important factor in patient selection. In this study, we propose a quantitative method (called SSI - Scaled Signal Intensity) for assessment of fibroid intensity and chances for treatment success.
Materials and Methods: The SSI is standardizing a fibroid mean MR T2W image signal intensity into a 0-100 scale, using reference intensities of skeletal muscle (as 0) and fat (as 100). Pretreatment SSI was retrospectively examined in 43 uterine fibroids in 40 premenopausal women who were treated using MRgFUS in a university affiliated center. We examined its correlation with the post treatment NPV ratios as continuous and dichotomous variable.
Results: Pre-treatment square root transformed SSI of uterine fibroids showed a significant inverse-correlation with NPV ratio (p < 0.05). When dichotomizing treatment response at 45% NPV ratio, the optimal cut off value of SSI was 16, which resulted good diagnostic performance using area under ROC curve (AUC) = 0.950 (95% CI, 0.837-0.993), sensitivity = 80.0%, specificity = 100.0%.
Conclusions: SSI shows significant correlation with the post treatment NPV ratios. This method can be suggested as an objective screening measure for patient selection in MRgFUS, in goal of achieving high NPV ratios.
